Jun 13 – 17, 2022
Berkeley, CA
US/Pacific timezone

Investigation of ground-state symmetry in the $^{71}$Kr/$^{71}$Br mirror pair

Not scheduled
1m
Berkeley, CA

Berkeley, CA

Lawrence Berkeley National Laboratory
Poster Poster Presentations Poster Session

Speaker

Ms Sanjanee Waniganeththi (University of Massachusetts Lowell)

Description

Properties of proton-emitting nuclei along the $N \sim Z$ line in the vicinity of the proton dripline, can be a useful probe of nuclear structure. In particular, the ground-state spins of the $^{71}$Kr/$^{71}$Br mirror pair have been under debate for several decades driven primarily by the closely spaced (E$_{x}$ = 10 keV) first-excited state in the $^{71}$Br mirror partner [1,2]. Additionally, a significant enhancement in the $\beta$-decay branching to excited states in $^{71}$Br had been suggested [3]. This should not be the case, however, if this system was a perfect mirror where the decay is expected to be dominated by a ground-state to ground-state transitions.

To explore these ground-state structures and the mirror symmetry in the $^{71}$Kr/$^{71}$Br system, we have performed detailed $\beta \gamma$ and $\beta p$ decay spectroscopy of $^{71}$Kr. A cocktail beam of heavy-ions, including $^{71}$Kr, was produced through projectile fragmentation of a 140-MeV/nucleon $^{92}$Mo primary beam, accelerated by the Coupled Cyclotron Facility at the National Superconducting Cyclotron Laboratory (NSCL), and impinged upon a 152.2-mg/cm$^{2}$ Be target. The secondary beam was analyzed by passing the ions through the A1900 fragment separator and further purified using the Radio Frequency Fragment Separator (RFFS). These ions were implanted into a DSSSD in the Beta-Counting Station (BCS) coupled to the Segmented Germanium Array (SeGA), enabling $\beta$ and $\beta$-delayed proton spectroscopy to be performed using implant-ion correlations. Branching to the ${5/2}^-$ 407-keV state in $^{71}$Br and a delayed-proton branch feeding the first-excited ${2}^+$ 945-keV state in $^{70}$Se were observed. A detailed analysis of the $\beta$ response of the setup was performed using $^{70}$Br ions that were simultaneously implanted. From this analysis we were able to determine absolute $\beta$ intensities as well as quantify an important source of systematic uncertainty in these types of decay experiments. Intensities of the measured $\gamma$ transitions were used to build the low lying $\beta$-decay scheme of $^{71}$Kr. Consequently, we find the observed delayed-proton decay to ${2}^+$ state in $^{70}$Se provides firm evidence that the ground-state spin of $^{71}$Kr must be $J > 3/2$, consistent with mirror symmetry of the $^{71}$Kr and $^{71}$Br ground-state pair both having $J^{\pi} = {5/2}^-$.

[1] M. Oinonen et al., Phys. Rev. C 56, 745 (1997).
[2] P. Urkedal and I. Hamamoto, Phys. Rev. C 58, R1889 (1998).
[3] S. M. Fischer et al., Phys. Rev. C 72, 024321 (2005).

We acknowledge support from the US DOE, Office of Science, Office of Nuclear Physics under award numbers DE-FG02-94ER40848 (UML), DE-AC02- 06CH11357 (ANL), as well as DE-FG02-88ER40387 and DE-SC0019042 (OU); the NNSA through award numbers DE-NA0003180 (NSSC), DE-NA0000979 (NSSC), DE-NA0003221, DE-NA0003909 and/or DE-NA0002132; and the NSF under contract numbers PHY-1-102511 and PHY 14-30152. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52- 07NA27344.

Primary authors

Ms Sanjanee Waniganeththi (University of Massachusetts Lowell) Prof. A.M. Rogers (University of Massachusetts Lowell) Dr D.E.M. Hoff (Lawrence Livermore National Laboratory, Livermore, CA 94550) Prof. C.J. Lister (University of Massachusetts Lowell)

Co-authors

Prof. P.C. Bender (University of Massachusetts Lowell) K. Brandenburg (Institute of Nuclear and Particle Physics, Department of Physics and Astronomy, Ohio University, Athens, OH 45701 ) K. Childers (Department of Chemistry, Michigan State University, East Lansing, Michigan 48824) J. Clark (Physics Division, Argonne National Laboratory, Argonne, IL 60439) A. Dombos (Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824 ) E. Doucet (University of Massachusetts Lowell) S. Jin (Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824 ) R. Lewis (Department of Chemistry, Michigan State University, East Lansing, Michigan 48824) S. Liddick (Department of Chemistry, Michigan State University, East Lansing, Michigan 48824) Z. Meisel (Institute of Nuclear and Particle Physics, Department of Physics and Astronomy, Ohio University, Athens, OH 45701 ) C. Morse (National Nuclear Data Center, Brookhaven National Laboratory, Upton, New York 11973) H. Schatz (JINA-CEE, Michigan State University, East Lansing, MI 48824) K. Schmidt (JINA-CEE, Michigan State University, East Lansing, MI 48824) D. Soltesz (Institute of Nuclear and Particle Physics, Department of Physics and Astronomy, Ohio University, Athens, OH 45701 ) S.K. Subedi (Institute of Nuclear and Particle Physics, Department of Physics and Astronomy, Ohio University, Athens, OH 45701 )

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